Caspase-10-mediated heat shock protein 90 beta cleavage promotes UVB irradiation-induced cell apoptosis.

Heat shock protein 90 beta (Hsp90 beta) is involved in many cellular functions. However, the posttranslational modification of Hsp90 beta, especially in response to apoptotic stimulation, is not well understood. In this study, we found that Hsp90 beta was cleaved by activated caspase-10 under UVB irradiation. Caspase-10 activation, in turn, depended on caspase-8, which cleaved caspase-10 directly. Autocrine secretion of FAS ligand and upregulated FAS expression induced by UVB irradiation contributed to activation of caspase-10, which cleaved Hsp90 beta at D278, P293, and D294. The downregulation of Hsp90 beta mediated by caspase-8-dependent caspase-10 activation promoted UVB-induced cell apoptosis.